Home » Public Forums » GMCnet » coach overheats after shutdown (what is normal transmission temp?)
| coach overheats after shutdown [message #84792] |
Sun, 16 May 2010 05:08  |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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When the coach is run long enough to reach operating temp, but not worked hard (there are no hills here) It will bubble and gurgle and sometimes blow steam out of the expansion tank.
I'm assuming this is the trans cooler holding stagnant heat against the radiator?
Is this indicative of a trans problem?
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: [GMCnet] coach overheats after shutdown [message #84793 is a reply to message #84792] |
Sun, 16 May 2010 06:47  |
Mr ERFisher
Messages: 7117
Registered: August 2005
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sounds more like air / exhaust getting into the cooling system
your expansion tank should always have fluid in it, and the radiator should
be always full to the top, (only check cold ;>)
If a GMC expansion tank, is ever empty, it says there is a leak in the
cooling system.
When the engine gets hot, the fluid expands and goes into the expansion
tank. When the engine cools, fluid is drawn back into the radiator. When
fluid is lost , eventually the overflow tank goes empty and the system does
not function.
The other thing that happens, is there is a head gasket leak, and exhaust
products go into the cooling system and bubbles out through the radiator /
overflow tank. You can have your radiator fluid tested for exhaust
products.
one thing for sure, keep looking till you find the problem.....
good luck
gene
On Sun, May 16, 2010 at 3:08 AM, dave silva <gmc@davesilva.com> wrote:
>
>
> When the coach is run long enough to reach operating temp, but not worked
> hard (there are no hills here) It will bubble and gurgle and sometimes blow
> steam out of the expansion tank.
>
> I'm assuming this is the trans cooler holding stagnant heat against the
> radiator?
>
> Is this indicative of a trans problem?
>
>
>
>
>
>
> --
> Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
> But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
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>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
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| Re: [GMCnet] coach overheats after shutdown [message #84794 is a reply to message #84792] |
Sun, 16 May 2010 06:50 |
Charles
Messages: 455
Registered: January 2004
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If I understand you correctly,. It sounds a little like head gasket problem.
How does it do on long drives. The mechanics really need more information.
Blacksmith hammer users like me will guess with little or no information.
Charles
>
>
>
> --
> Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
> But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
> _______________________________________________
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Charles Wersal
Duncanville, Texas
26 foot 1975 Glenbrook
Pandora's Box
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| Re: [GMCnet] coach overheats after shutdown [message #84797 is a reply to message #84793] |
Sun, 16 May 2010 07:27 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
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On a long drive it maintains temp. I don't rmember what the operating temp was on the last long drive but it was in a normal range.
I stopped, shut it doan, did a walk around, and after a minute or two I heard gugling and steam from the expansion tank.
The key detail is that is was not hot until a bit after it was shut down.
I have seen this on other vehicles. Hot transmission fluid stops moving in the radiator and with o circulation the coolant overheats.
The question is- is it a trans heat problem or a cooling system problem?
I believe serious cooling problems like a head gasket leak would manifest other ways on a long drive.
dave
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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| Re: [GMCnet] coach overheats after shutdown [message #84800 is a reply to message #84793] |
Sun, 16 May 2010 07:42 |
scott cowden
Messages: 170
Registered: February 2004
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Your overheating after shut down may not necessarily be an indicator of trouble, but it is an indication of how hot the engine is running.
When the engine is shut down, of course, coolant no longer flows over the block and through the heads to cool them, but the latent heat remains in the metal. The coolant is no longer passing through the engine but is now 'in place,' or , 'static,' if you like and absorbing heat.
If the residual heat in the engine metal parts is greater than the boiling point of the coolant, boiling and steam release can result.
You may also have too much water in your coolant. See number 2 below.
What I suggest you do as first steps before getting too deep into this symptom is to inspect your coolant.
It should be:
1: Clean. Whatever color it's supposed to be, it should still be. [green/yellow/red, whatever]. If it's muddy looking, it's way overdue for replacement. Five years is the absolute max in age, 2-3 years in high stress applications like a motorhome is best. Not changing coolant on a regular basis can also damage internal engine parts and even head gaskets as the anti-corrosion properties wear off and cause corrosion between dissimlar metals.
2: It should have appropriate heating cooling properties. Spend $5 and get a coolant tester. Properly mixed with water, a 50/50 mixture, it will have a freezing point of -40 deg. When at this mixture it also has a boiling point higher than regular water. Too much water drops the boiling point.
3: Good radiator cap. A radiator cap controls the boiling point of the coolant by using pressurization. Off the top of my head, I think a GMC should have a 9 lb cap. [please check that before buying a new one to be sure] If the caps spring is weak, it will release early and can cause boilover both in running and in the condition we're discussing.
You asked about transmission problems overheating the coolant. I've not seen this happen, but hey, everyday is a new day. Is that part of your question related to a transmission issue? A transmission cooler is always a good idea on a GMC, although I've never installed one myself. [note to self, put that on the list!]
Just thoughts for you.
Scott '74 Glacier 'Living in my coach this summer at a new job in SUDBURY', ON, Canada
> sounds more like air / exhaust getting into the cooling system
>
> your expansion tank should always have fluid in it, and the radiator should
> be always full to the top, (only check cold ;>)
>
> If a GMC expansion tank, is ever empty, it says there is a leak in the
> cooling system.
>
> When the engine gets hot, the fluid expands and goes into the expansion
> tank. When the engine cools, fluid is drawn back into the radiator. When
> fluid is lost , eventually the overflow tank goes empty and the system does
> not function.
>
> The other thing that happens, is there is a head gasket leak, and exhaust
> products go into the cooling system and bubbles out through the radiator /
> overflow tank. You can have your radiator fluid tested for exhaust
> products.
>
> one thing for sure, keep looking till you find the problem.....
>
> good luck
> gene
>
>
> On Sun, May 16, 2010 at 3:08 AM, dave silva <gmc@davesilva.com> wrote:
>
> >
> >
> > When the coach is run long enough to reach operating temp, but not worked
> > hard (there are no hills here) It will bubble and gurgle and sometimes blow
> > steam out of the expansion tank.
> >
> > I'm assuming this is the trans cooler holding stagnant heat against the
> > radiator?
> >
> > Is this indicative of a trans problem?
> >
> >
> >
> >
> >
> >
> > --
> > Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
> > But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
> > _______________________________________________
> > GMCnet mailing list
> > List Information and Subscription Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
>
>
>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] coach overheats after shutdown [message #84805 is a reply to message #84797] |
Sun, 16 May 2010 08:36 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
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| hertfordnc wrote on Sun, 16 May 2010 07:27 |
On a long drive it maintains temp. I don't rmember what the operating temp was on the last long drive but it was in a normal range.
I stopped, shut it doan, did a walk around, and after a minute or two I heard gugling and steam from the expansion tank.
The key detail is that is was not hot until a bit after it was shut down.
I have seen this on other vehicles. Hot transmission fluid stops moving in the radiator and with o circulation the coolant overheats.
The question is- is it a trans heat problem or a cooling system problem?
I believe serious cooling problems like a head gasket leak would manifest other ways on a long drive.
dave
|
where is the temp needle on your gauge? just over half way is the boil over point. there is another temp sender that will read higher and look more "normal" than the OEM sender. i couldn't find my link for it. maybe Gene has it.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: [GMCnet] coach overheats after shutdown [message #84807 is a reply to message #84793] |
Sun, 16 May 2010 08:35 |
Steven Ferguson
Messages: 3447
Registered: May 2006
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Senior Member |
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Something else to consider here is the size of the expansion tank (aka
surge tank). If it has been replaced in the past with one that does
not have adequate volume, it will over flow when it's doing it's job.
Next time you get the coach heat soaked, leave it running and check
the surge tank level. The original one holds well over a quart. Most
of the aftermarket replacements are adequate for a car, but not a
motorhome application. Lastly, if you arrive at your destination
after a hard pull, let the engine idle for a while and the coolant
temp stabilize.
If your fan clutch is inop, you will also see these same symptoms.
That overflow will blow steam and water even after a short, no load
drive.
On a cold start, are you able to hear the fan clutch engage for about
1-2 minutes before it begins to disengage?
On Sun, May 16, 2010 at 4:47 AM, Mr.erf ERFisher <mr.erfisher@gmail.com> wrote:
> sounds more like air / exhaust getting into the cooling system
>
> your expansion tank should always have fluid in it, and the radiator should
> be always full to the top, (only check cold ;>)
>
> If a GMC expansion tank, is ever empty, it says there is a leak in the
> cooling system.
>
> When the engine gets hot, the fluid expands and goes into the expansion
> tank. When the engine cools, fluid is drawn back into the radiator. When
> fluid is lost , eventually the overflow tank goes empty and the system does
> not function.
>
> The other thing that happens, is there is a head gasket leak, and exhaust
> products go into the cooling system and bubbles out through the radiator /
> overflow tank. You can have your radiator fluid tested for exhaust
> products.
>
> one thing for sure, keep looking till you find the problem.....
>
> good luck
> gene
>
>
> On Sun, May 16, 2010 at 3:08 AM, dave silva <gmc@davesilva.com> wrote:
>
>>
>>
>> When the coach is run long enough to reach operating temp, but not worked
>> hard (there are no hills here) It will bubble and gurgle and sometimes blow
>> steam out of the expansion tank.
>>
>> I'm assuming this is the trans cooler holding stagnant heat against the
>> radiator?
>>
>> Is this indicative of a trans problem?
>>
>>
>>
>>
>>
>>
>> --
>> Free to good home- the rest of a 1974 GMC. good for extension, or trailer.
>> But you gotta' take the whole thing -zip 27944- rear wheels, glass, etc.
>> _______________________________________________
>> GMCnet mailing list
>> List Information and Subscription Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source
www.bdub.net/ferguson/
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| Re: coach overheats after shutdown [message #84816 is a reply to message #84792] |
Sun, 16 May 2010 09:39 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| hertfordnc wrote on Sun, 16 May 2010 06:08 |
When the coach is run long enough to reach operating temp, but not worked hard (there are no hills here) It will bubble and gurgle and sometimes blow steam out of the expansion tank.
I'm assuming this is the trans cooler holding stagnant heat against the radiator?
Is this indicative of a trans problem?
|
Dave,
By Expansion Tank, I am going to guess you mean the overflow bottle as there is no expansion tank on a stock GMC.
It is not likely to be an indicator of a transmission problem.
If you switch the ignition back on and do not restart, what does the temperature gauge indicate? If it is not climbing, even with the OE temperature sensor, get the cap relief pressure checked.
If this is correct then:
It is likely to be an indicator of a circulation problem in the engine itself. This could well be blockage in the system or a coolant circulating pump (water pump) that is not effective and so is allowing the castings to "hot spot".
The Blacksmith that needs more information - Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] coach overheats after shutdown [message #84820 is a reply to message #84816] |
Sun, 16 May 2010 10:00 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Matt,
Dave's not talking about GMC as he has a Revcon and it might have an
expansion tank and a water bottle.
Regards,
Rob Mueller
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Matt Colie
Sent: Monday, 17 May 2010 12:40 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] coach overheats after shutdown
Dave,
By Expansion Tank, I am going to guess you mean the overflow bottle as there
is no expansion tank on a stock GMC.
It is not likely to be an indicator of a transmission problem.
If you switch the ignition back on and do not restart, what does the
temperature gauge indicate? If it is not climbing, even with the OE
temperature sensor, get the cap relief pressure checked.
If this is correct then:
It is likely to be an indicator of a circulation problem in the engine
itself. This could well be blockage in the system or a coolant circulating
pump (water pump) that is not effective and so is allowing the castings to
"hot spot".
The Blacksmith that needs more information - Matt
--
Matt & Mary Colie
'73 Glacier 23 Chaumiere (say show-me-air)
SE Michigan - DTW 3.2/4R
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] coach overheats after shutdown [message #84831 is a reply to message #84820] |
Sun, 16 May 2010 11:41 |
hertfordnc
Messages: 1164
Registered: September 2009
Location: East NC
Karma: 0
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I'm sorry, i forgot to include the Revcon Disclaimer.
For those have not been following the saga, i bought a Revcon last year and then acquired a rusted GMC for parts and to part out. The process left me pretty familiar with the differences and similarities between the two coaches.
Generally speaking, the systems all work the same. Revcon is almost entirely Toronado with a few beefed up components. The carb is not the same, but it's still a quadrajet, the master cylinder is different but the system is the same with the same combination valve, etc,
So i am fairly certain the cooling system functions the same.
Thanks
Dave & Ellen Silva
Hertford, NC
76 Birchaven, 1-ton and other stuff
Currently planning the Great american Road Trip Summer 2021
It's gonna take a lot of Adderall to get this thing right.
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